1465results about "Line-faulsts/interference reduction" patented technology

A wireless communication system can comprise two or more antennas that interfere with one another via free space coupling, surface wave crosstalk, dielectric leakage, or other interference effect. The interference effect can produce an interference signal on one of the antennas. A cancellation device can suppress antenna interference by generating an estimate of the interference signal and subtracting the estimate from the interference signal. The cancellation device can generate the estimate based on sampling signals on an antenna that generates the interference or on an antenna that receives the interference. The cancellation device can comprise a model of the crosstalk effect. Transmitting test signals on the communication system can define or refine the model.

Methods, systems, and apparatuses for down-converting an electromagnetic (EM) signal by aliasing the EM signal are described herein. Briefly stated, such methods, systems, and apparatuses operate by receiving an EM signal and an aliasing signal having an aliasing rate. The EM signal is aliased according to the aliasing signal to down-convert the EM signal. The term aliasing, as used herein, refers to both down-converting an EM signal by under-sampling the EM signal at an aliasing rate, and down-converting an EM signal by transferring energy from the EM signal at the aliasing rate. In an embodiment, the EM signal is down-converted to an intermediate frequency (IF) signal. In another embodiment, the EM signal is down-converted to a demodulated baseband information signal. In another embodiment, the EM signal is a frequency modulated (FM) signal, which is down-converted to a non-FM signal, such as a phase modulated (PM) signal or an amplitude modulated (AM) signal.

Techniques for calculating the system characteristic of the adaptive filtering used for equalization and echo-suppression in a digital communications receiver, such as one used for receiving over-the-air broadcast digital television signal, are described. In these techniques, the system characteristic of the adaptive filtering is calculated from the discrete Fourier transform of successive portions of the input signal supplied to the adaptive filtering and from the discrete Fourier transform of corresponding portions of the transmitted signal, as estimated in the receiver. Receivers for implementing these techniques in various ways are also disclosed.

The equalizer of the present invention operates on input multipath signal samples, preferably at chip or sub-chip resolution, to remove or substantially cancel the effects of one or more secondary signals from the main path signal. Using predetermined path information for one or more of the secondary path signals, including magnitude, phase, and time offset relative to the main path signal, the equalizer compensates input multipath signal samples by subtracting estimated secondary signal values from the input samples. For each input sample, the equalizer forms a sliced sample, where the sliced sample represents a nominal phase value defined by the modulation scheme used in the original chip or symbol transmission that is closest in value to the actual phase of the input sample. These sliced samples are held in a running buffer and used, in combination with the predetermined path information and scaling logic, to form the estimated secondary signal values for compensating the input samples.

Systems and methods for providing notifications to players of a gaming console of messages and system notifications. A controller and the gaming console include a four quadrant LED indicator. Each quadrant of the ring may be illuminated individually or together using an LED to indicate the messages and notifications. The quadrants may be illuminated in one of three colors and/or in patterns to indicate different types of notifications. Onscreen displays may be used to supplement the LED indicators to convey information to users. A method of binding and discovering a controller is also provided where the controller may be bound to a gaming console. After a controller is bound to a console, the controller may be discovered by the gaming console where it is assigned a virtual port and enabled for game play.

A system and method are described for compensating for frequency and phase offsets in a multiple antenna system (MAS) with multi-user (MU) transmissions (“MU-MAS”). For example, a method according to one embodiment of the invention comprises: transmitting a training signal from each antenna of a base station to one or each of a plurality of wireless client devices, one or each of the client devices analyzing each training signal to generate frequency offset compensation data, and receiving the frequency offset compensation data at the base station; computing MU-MAS precoder weights based on the frequency offset compensation data to pre-cancel the frequency offset at the transmitter; precoding training signal using the MU-MAS precoder weights to generate precoded training signals for each antenna of the base station; transmitting the precoded training signal from each antenna of a base station to each of a plurality of wireless client devices, each of the client devices analyzing each training signal to generate channel characterization data, and receiving the channel characterization data at the base station; computing a plurality of MU-MAS precoder weights based on the channel characterization data, the MU-MAS precoder weights calculated to pre-cancel frequency and phase offset and/or inter-user interference; precoding data using the MU-MAS precoder weights to generate precoded data signals for each antenna of the base station; and transmitting the precoded data signals through each antenna of the base station to each respective client device.

A novel and useful apparatus for and method of Gaussian Minimum Shift Keying (GMSK) single antenna interference cancellation (SAIC) for use in a digital receiver. The invention comprises an interference mitigation module that treats the problem of GMSK SAIC in a blind manner. The interference mitigation mechanism is operative to compensate for the co-channel interference added in the communications channel which is subject to multipath propagation and fading, receiver filter and any pre-channel estimation filtering. The interference mitigation module takes advantage of the spatial diversity making up multiple branches of the received signal. The branches comprise the in-phase and quadrature elements of the received signal, the sampling phases if over sampling is applied (i.e. T/m sampling) and/or multiple antennas. The invention utilizes the spatial diversity of these multiple representations of the received signal and combines (i.e. collapses) the information in the plurality of branches into a single branch that is input to the equalizer.

In bus communications methods and apparatus, a first set of physical signals representing the information to be conveyed over the bus is provided, and mapped to a codeword of a sparse signaling code, wherein a codeword is representable as a vector of a plurality of components, some of which are quiescent components and some of which are non-quiescent components, wherein the number of quiescent components and non-quiescent components meet a sparseness requirement.

A multistage interference canceller and method for removing interference between users and multipath interference from received signals in multiple stages includes a plurality of despreading units which produce a received symbol vector and an estimated channel value, a synthesis unit which synthesizes the received symbol vector, an amplitude of the received symbol vector and the amplitude of the estimated value from each reverse spreading unit, and a decision unit which executes a hard decision and a soft decision according to a result of comparing the total amplitude of the received symbol vector and the total amplitude of the estimated channel value.

A method and apparatus for spatial multiplexing and demultiplexing of radio signals. A multichannel transmitter and receiver is integrated in a base station and coupled to an antenna array. Using digital radio signals containing previously known or non-Gaussian sequences and arranged in frames, the spatial information about each mobile unit is estimated on the basis of the signal received by the receiver for the reception and transmission frequencies. This is done by known sequences or by blind source separation methods. The respective paths of each mobile unit with the power above a predetermined threshold is isolated by spatial filtering in the presence of multiple channel paths in order to provide spatial demultiplexing. Simultaneously, the intended signal is transmitted in the direction of the main path of each mobile unit while protecting each mobile unit from signals transmitted in the direction of other mobile units by spatial filtering with cancelling constraints in order to provide spatial multiplexing.

The present invention relates to a blind adaptive filter for narrowband interference cancellation, which includes an adaptive filter, a delay unit coupled to the adaptive filter for generating a delayed signal with a predetermined delay length from the output signal of the adaptive filter, and an error calculation unit coupled to the adaptive filter and the delay unit. The error calculation unit compares the output signal from the adaptive filter and the delayed signal from the delay unit to extract error information, and feedback the first error information to the adaptive filter. The first error information is formed of a transfer function including a number of coefficients, and used to adjust the adaptive filter and remove interference in the next input signal. The disclosed technique is also applicable in wideband receivers, as well as resisting multiple strong narrowband interferences having a frequency sweep rate of tens of milliseconds.

A multi-carrier communication system such as an OFDM or DMT system has nodes which are allowed to dynamically change their receive and transmit symbol rates, and the number of carriers within their signals. Changing of the symbol rate is done by changing the clocking frequency of the nodes' iFFT and FFT processors, as well as their serializers and deserializers. The nodes have several ways of dynamically changing the number of carriers used. The selection of symbol rate and number of carriers can be optimized for a given channel based on explicit channel measurements, a priori knowledge of the channel, or past experience. Provision is made for accommodating legacy nodes that may have constraints in symbol rate or the number of carriers they can support. The receiver can determine the correct symbol rate and number of carriers through a priori knowledge, a first exchange of packets in a base mode that all nodes can understand, or an indication in the header of the data packet which is transmitted in a base mode of operation that all nodes can understand.

A communication system uses analog and digital circuits along the same data path in a manner that permits the analog circuitry to avoid adverse affects caused by the digital circuitry. Consistent with one embodiment directed to a signal processing system that detects faint incoming signals, the analog and digital circuits are implemented on a single piece of silicon. In such signal processing systems, noise generated by digital processing blocks can degrade the performance of sensitive analog portions. The effective noise is reduced by causing the analog and digital portions of the system to function during separate time intervals. The noise-generating portions of the system may then be turned off during a first data-communication interval while the analog block operates. The data acquired during this period is stored for subsequent processing by the digital portion during a second shorter data-communication interval. Other aspects are applicable to reception arrangements in which part of the incoming signal may be disregarded without significant degradation in performance of the rest of the system, and other aspects are directed to transmission arrangements in which the inverse of the above reception arrangement is used.

A method is provided for an equalization strategy for compensating channel distortions in a dual-polarization optical transport system wherein the received signal includes a complex signal of a first transmitted polarization component and a complex signal of a second transmitted polarization component. In a first step, a blind self-recovery mode used a blind adaptation algorithm in calculating and modifying multiple complex equalizer transfer function coefficients to enable recovery of only the complex signal of the first transmitted polarization component. By recovering only a single polarization component in the first step the degenerate case of recovering only a single transmitted signal at both polarization component outputs of an equalizer is prevented. In a second step, equalization is performed in a training mode for calculating and modifying the multiple complex equalizer transfer function coefficients to enable recovery of the complex signals of the first and second transmitted polarization components. In a third step, equalization is performed in a data directed mode for continuing to calculate and modify the multiple complex equalizer transfer function coefficients to ensure continued recovery of the complex signals of the first and second transmitted polarization components. The method is suited for a digital signal processing implementation in a coherent receiver when a modulation scheme used on a transmitted signal is quadriphase-shift keying (QPSK). In other embodiments, the method can be used with modulation schemes such as binary PSK, M-ary PSK where M>4, or Quadrature Amplitude Modulation (QAM).

A device for identifying interference source in wireless communications is provided, including a correlation compound module, a matching and screening module, a statistical analysis module, and a match identification module. The correlation compound module uses the time of arrival (TOA) of the burst as the synchronization basis to compound the correlated frequency word, time difference of arrival (TDOA) word, amplitude word and angle of arrival (AOA) word to form a burst descriptor word (BDW). The matching and screening module uses the BWD to match the burst library to screen out the non-interference sources. The statistic analysis module uses the screened outcome for statistical analysis, and obtains a source discriminator file (SDF). The matching and identification module uses the SDF to search the interference source library for matching and obtains an identification result.

Potential interference is reduced in an impulse radio. A signal including an impulse signal and potential interference is received by the impulse radio. The impulse signal includes a sequence of impulses. The sequence of impulses of the received signal is sampled at a sequence of data sample times to produce a sequence of data samples. The received signal is also sampled at a plurality of time offsets from each of the data sample times to produce a plurality of nulling samples corresponding to each of the data samples. A separate sequence of nulling samples for each of the time offsets is thereby produced. Each of the data samples is then separately combined with a corresponding nulling sample from each of the separate sequences of nulling samples to produce a separate sequence of adjusted samples corresponding to each of the time offsets. A separate quality metric, representative of a signal-to-interference level, is then determined for each of the separate sequences of adjusted samples. A preferred sequence of samples is selected for further signal processing based on the determined quality metrics. Alternatively or additionally, one of the plurality of time offsets is selected as the preferred time offset based on the determined quality metrics.

A beam formation circuit and an apparatus and a method of receiving radio frequency signals making use of a smart antenna are described in which the amount of computation tasks required for the weight calculation is significantly reduced. In realizing the directivity of the smart antenna, the output signals corresponding to a plurality of sub-carriers are weighted with a common antenna weight for each of the antenna elements.

Methods and systems are provided for reducing interference across coverage cells using base stations interconnected by a packet network. A wireless device monitors the channel signal strength of its serving cell and its neighboring cell. The serving cell collects measurements from the wireless devices within its cell and informs its neighboring cell when one of the wireless device may be causing significant interference to the neighboring cell. The neighboring cell collects this information and executes a multi-user detection and cancellation algorithm on a subset of these interfering wireless devices.

A system and method for transmitting a plurality of input data symbol sub-streams over a plurality of spatial-subspace channels of a sub-carrier between a transmitter and the receiver. The plurality of input data symbol sub-streams are partitioned in a plurality of super-frames of data and weighted by a weight matrix derived from the singular value decomposition of a channel matrix corresponding to the sub-carrier by applying a partial SVD algorithm. The transmitter further inserts subspace training symbols into the plurality of input data symbol sub-streams and the receiver periodically processes the sub-space training symbols during each super-frame of the plurality of super-frames for estimating output data related to the input data symbol stream.

A Fiber-wireless uplink consists of a wireless channel followed by a radio-over-fiber (ROF) link. Typically, nonlinear distortion of the ROF link is the major concern when the radio frequency is only a few GHz. This especially severe in the uplink, because of the multipath fading of the wireless channel. A Hammerstein type decision feedback equalizer is described for the fiber wireless uplink, that compensates for nonlinear distortion of the ROF link as well as linear dispersion of the wireless channel. Since the linear and nonlinear parts of the receiver are separated, tracking the fast changing wireless channel is virtually independent of compensating for the relatively static nonlinearity. Analytical results show that the receiver provides excellent compensation with notably less complexity.

A system for compensating for in-phase and quadrature (I/Q) imbalances for multiple antenna systems (MAS) with multi-user (MU) transmissions (defined with the acronym MU-MAS), such as distributed-input distributed-output (DIDO) communication systems, comprising multicarrier modulation, such as orthogonal frequency division multiplexing (OFDM). For example, one embodiment of the system comprises one or more coding modulation units to encode and modulate information bits for each of a plurality of wireless client devices to produce encoded and modulated information bits; one or more mapping units to map the encoded and modulated information bits to complex symbols; and a MU-MAS or DIDO IQ-aware precoding unit to exploit channel state information obtained through feedback from the wireless client devices to compute MU-MAS or DIDO IQ-aware precoding weights, the MU-MAS or DIDO IQ-aware preceding unit precoding the complex symbols obtained from the mapping units using the weights to pre-cancel interference due to I/Q gain and phase imbalances and/or inter-user interference.

Methods and apparatuses for reducing DC offsets in a communication system are described. In a first aspect, a feedback loop circuit reduces DC offset in a wireless local area network (WLAN) receiver channel. The frequency response of the feedback loop circuit can be variable. In a second aspect, a circuit provides gain control in a WLAN receiver channel. The stored DC offset is subtracted from the receiver channel. First and second automatic gain control (AGC) amplifiers are coupled in respective portions of the receiver channel. In a third aspect, a feedback loop circuit reduces DC offset in a WLAN receiver channel. The feedback loop circuit includes a storage element that samples and stores receiver channel DC offset. The loop is opened, and the DC offset stored in the storage element is subtracted from the receiver channel. Circuits for monitoring DC offset, and for providing control signals for controlling the frequency response of the DC offset reducing circuits are also provided.

An apparatus and method for transmitting Walsh information over a packet data control channel in a base station of a mobile communication system that transmits packet data and has the packet data control channel for transmitting control information related to transmission of packet data. Receivers decode reverse ACK channel (R-ACKCH) signals received from corresponding mobile stations, and count the number of NAKs from the decoded information. A Walsh mask broadcasting controller receives the number of NAKs from the receivers, and outputs a Walsh mask information broadcasting enable signal if the number of NAKs is larger than a predetermined threshold. A transmitter generates and broadcasts Walsh mask information of the base station upon receiving the Walsh mask information broadcasting enable signal.

A multimode wireless receiver circuit (10) includes multi-receiver control and interference detection logic (50) and least two separate receivers: a first receiver (20) associated with a first radio access technology and a second receiver (30) associated with a second radio access technology. The multi-receiver control and interference detection logic (50) simultaneously controls the second receiver (30) to detect an interference blocker signal (100), while the first receiver (20) receives at least a portion of the wireless signal (80) and the interference product signal (90). In response to the second receiver (30) detecting the interference blocker signal (100), the multi-receiver control and interference detection logic (50) adjusts at least one operating condition of the first receiver (20) such that the interference product signal (90) received by the first receiver (20) is reduced.

A linear turbo-equalizer for use in a CDMA receiver equalizes a despread received signal (rather than the spread received signal) to suppress self-interference resulting from coupling between transmitted symbols. In an example implementation, a linear equalizer based on a generalized-Rake (G-Rake) receiver design uses decoder feedback in forming Rake combining weights as well as in forming a self-interference estimate removed from the equalizer signal provided to the decoder. Preferably, turbo de-coding is also performed. In that case, each turbo-decoder component preferably executes one pass before feeding back information to the equalizer. This ensures that the turbo-decoder does not prematurely lock onto an incorrect code word before feeding back extrinsic information to the equalizer.

A system and method for mapping radio-frequency (RF) noise, and estimating channel quality in a multi-channel ultra-wideband communication system is provided. One method includes placing a plurality of time bins within a plurality of time frames and assigning a plurality of UWB communication channels comprising selected time bins. RF noise amplitude data is then sampled from selected time bins. The sampled RF noise amplitude data from the time bins is then averaged, thereby obtaining an average RF noise amplitude in each of the plurality of channels. The RF noise amplitude indicates the amount of RF noise present in a channel. The channels may then be ranked based on the characteristics of the RF noise.

An efficient telecommunications receiver system for accurately decoding a received composite signal having a data signal component and a pilot signal component. The receiver system includes a first circuit for receiving the composite signal and extracting a pilot signal and a data signal from received composite signal. A second circuit calculates a log-likelihood ratio as a function of a channel estimate based on the pilot signal. A third circuit scales the log-likelihood ratio by a predetermined log-likelihood ratio scaling factor and provides an accurate log-likelihood value in response thereto. A fourth circuit decodes the received composite signal based on the accurate log-likelihood value and the data signal. In a specific embodiment, the pilot signal and the data signal comprise pilot samples and data samples, respectively. The third circuit includes a carrier signal-to-interference ratio circuit for computing a first signal-to-interference ratio and a second signal-to-interference ratio based partly on the pilot signal. The first signal-to-interference ratio is based on the data samples, and the second signal-to-interference ratio is based on the pilot samples. The first signal-to-noise ratio and the second signal-to-noise ratio provide input to a circuit for computing the predetermined log-likelihood ratio scaling factor that is included in the third circuit. In a more specific embodiment, the first circuit includes a despreader for despreading the received composite signal in accordance with a predetermined spreading function and providing a despread signal in response thereto. The spreading function is a pseudo noise sequence or a Walsh function. The first circuit further includes a decovering circuit that extracts the pilot signal and the data signal from the despread signal. In the illustrative embodiment, the accurate receiver system further includes a circuit for generating a rate and/or power control message and transmitting the rate and/or power control message to an external transceiver in communication with the efficient receiver system.

A computer system with a semi-differential bus-signaling scheme is described. The computer system includes a transmitter coupled to a common bus. The transmitter sends clock signals and a data signal to logic-comparing devices within a receiver. The logic-comparing devices compare the data signal to a reference voltage while comparing the clock signals to each other. After the comparison, the clock signals can be used to capture the data into a retiming circuit.

By virtue of one embodiment of the present invention, dynamic signal to noise ratio measurements made on received signals are used to identify degraded segments of a channel. The degraded segments are then no longer used for transmitting payload data. In the context of an orthogonal frequency division multiplexing (OFDM) communication system, degraded OFDM subchannels, as determined on a real-time basis, are not used to transmit payload data. In an OFDM network where access is shared in the time domain among multiple transmitters and a single allocable time slot includes an integer number of OFDM bursts, the medium access control layer adjusts packet length, and therefore the amount of data to be included in a given slot, in response to the fluctuating number of available subchannels.

The present invention provides a synchronous demodulation apparatus of a base transceiver station in an Interim Standard-2000 (IS-2000) system, including a first synchronous demodulation unit, a received signal delay unit, an interference signal regeneration unit and a second synchronous demodulation unit. In comparison with an asynchronous demodulation apparatus used in an Interim Standard-95 (IS-95), it is possible for the inventive apparatus to improve a reception function approximately 3dB and ultimately increase the number of subscribers.